Emily Dickinson Lexicon

BAY, a. [Fr. bai or baie; It. baio; Sp. bayo; L. badius. Class Bd.]

Red, or reddish, inclining to a chestnut color; applied to the color of horses. The shades of this color are called light bay, dark bay, dappled bay, gilded bay, chestnut bay. In popular language, in England, all bay horses are called brown. – Johnson. Encyc.